An Application of Two-Phase DC Chopper Motor Drive

During the past ten years the Army has invested a sizable effort into new systems configurations and development programs to improve ground vehicle mobility. United States Army Mobility Equipment Research and Development Center (USAMERDC), Fort Belvoir, Va., has been particularly interested in an improved vehicle mobility for off-highway vehicles, amphibians, and engineer equipment through electrical propulsion. Such drive systems incorporating individual wheel controls provide improved mobility over all types of terrain, simplified supply logistics, and permit a more functional vehicle design and construction. Past experience in industry and in the government has shown that the dc motor propulsion drive is inherently simple to install and to maintain. The dc motor is somewhat heavier than comparable ac motors due to motor speed limitations; however, the dc machine, particularly the series field motor, requires relatively simple power controls since the power is processed by the motor's own commutator. Commercial dc traction motors have an inherent high-torque starting characteristic which is mandatory for engineer-type vehicle propulsion applications. In the midspeed range however, presently available dc motor propulsion drives under consideration for the Anny have unsatisfactory acceleration performance when compared to conventional mechanical drive systems comprised of a spark or compression ignition engine and a multispeed transmission. In this context, the paper discusses this Center's experimental solid-state controller and the method employed to improve the acceleration or peak power propulsion profile of an electric vehicle drive using dc series field motors.